Two plane mirrors are inclined at an angle θ. A ray of light is reflected from the first mirror and is then incident on the second mirror from which it is again reflected. What is deviation of incident ray?

 A mirror with a flat surface is a plane mirror that reflects light and produces a virtual image without the interference of an inward or outward curve is called a plane mirror.

Solution

As per the figure 

Let us assume the two incident angles

∠BAD=x

∠ABD=y 

We observe that
⇒∠OBA=90−y

∠OAB=90−x
ΔOAB=>θ+90−y+90−1=180
⇒x+y=θ
Total deviation is 2(90−x)+2(90−y)
=360−2(x+y)
=360−2θ

Answer

The deviation of incident ray =360−2θ